Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1998-02-17
2001-05-08
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S089000, C385S076000, C385S014000
Reexamination Certificate
active
06229942
ABSTRACT:
The invention relates to optical connector means for flexfoils, i.e. flexible sheets having optical waveguides arranged therein or thereon, the connector means being intended for e.g. connection to circuit boards and to backplanes.
BACKGROUND
As the data rates of computers, telecommunication, etc. arm ever increasing, optical communication, well established since long times in long distance broad band communications, is also being introduced for short range applications inside exchanges and computers, etc. For such applications the number of optical interconnections may become significant. Thus there exist a need for controlling and handling the routing of optical fibers or generally optical wave guides.
One practical approach to his is to use a separate optical level to house all the optical connections in the shape of an optical flexfoil having internal fibers or waveguides. By using optical connectors at the ends of the fibers/waveguides connections can be established to electro-optical devices and to external devices such as electrical backplanes.
The company AT&T has in a few patents, in particular in U.S. Pat. No. 5,204,925 for Bonnani et al., described the use of optical fiber flexfoils having tabs extending from the man body of the flexfoils and being capable of being twisted in a 90° angle in relation to the main body in order to accomplish an “edge to edge” backplane connection where the edges of the main bodies of the circuit boards and the main bodies of the backplane flexfoils are located perpendicularly to each other. For general systems this is an unusual configuration as compared to the more familiar one where the circuit boards extend perpendicularly from the backplane. However, such a solution could possibly be accomplished in the AT&T solution by folding the flexfoil.
However, the AT&T concept has one severe limitation in that it is not possible to accomplish a connection of an edge of a circuit board at several distinct positions to the backplane using the simple geometrical solution disclosed. By having further prolonged tabs which both can be both twisted and bent, such connections would in principle be possible but the edge length of the backplane foil from which the tabs extend would be much larger than the otherwise required separation between or spacing of the boards, this effect being even more pronounced in the case where more tabs are required per circuit board.
In U.S. Pat. No. 5,259,051 for Burack et al., also assigned to AT&T, a method of making an optical flexfoil is disclosed. In the embodiment described in conjunction with
FIG. 7
, a base foil is used having tabs extending from a main body of the foil. On this foil one or more optical fibers are routed and then cut and thereupon possibly, a top foil can be applied. Finally the tab edges and the border are cut.
SUMMARY
It is an object of the invention to provide connector means for optical waveguides on flexfoils allowing a compact configuration of the flexfoils and also allowing a flexible layout of backplanes and circuit boards, with which the flexfoils are to be used.
It is a fiber object of the invention to provide a flexfoil having arrangements for allowing that connector tabs are polished in a simple apparatus.
Thus, the problem to be solved by the invention is how to make a flexfoil that can easily be handled, that allows external connections at any place of the flexfoil and that allows that a polishing of waveguide ends at connector tabs is made in a simple manner.
In an optical flexfoil comprising optical waveguides such as optical fibers ends of the optical fibers can be located at both inner and edge positions of the flexfoil. Cut-outs are formed around such fiber ends to form tabs so that the ends of the fibers are located at the exterior edges of the tabs. The tabs are made so that they can be bent from the plane of the main body of the flexfoil and thus to project from his plane. The tabs are then located at basically internal positions of the flexfoil, i.e. so that no portions of the tabs extend beyond the edges of the flexfoil in the plane thereof. In polishing the ends of the fibers at the tab edges hem tabs are bent to have their exterior regions located e.g. perpendicularly to the plane of the flexfoil and are rigidly retained in this position during the polishing is operation. Before the polishing operation the tab ends can have been provided with suitable optical connectors.
Thus, such tabs cut out from the body of the flexfoil can be used e.g. both as a means of connecting to electro-optical devices on a circuit board located immediately at one of the large surfaces of the flexfoil body and as a means of obtaining a 90° deflection from a flexfoil acting as an optical backplane oriented in parallel to a conventional electrical backplane and located at the rear side thereof. With this type of topology it is then possible to obtain multiple optical connection points between the backplane and a circuit board, not requiring additional edge length of the backplane flexfoil for obtaining a plurality of tabs per board. By making openings in the electrical backplane through which tabs bent out of the optical backplane extend it is then possible to obtain a mixture of electrical and optical connection sites at the board edge. By his topology also, optical connectors at the tab ends of e.g. multichannel type will be oriented in parallel to the circuit board plane without requiring any twist of the tabs.
As a cut out tab necessarily removes surface from the flexfoil, where waveguides otherwise could be located, it is required that the tabs are not unnecessarily long and thus that they can be bent in a small radius out of the flexfoil main plane. For an optical backplane this is also required for obtaining a reasonable spacing of the printed circuit boards which are to be connected to the backplane. It is also required that the fibers routed in the flexfoil can be routed at small routing radii around the cut-outs made for the tabs since otherwise large routing radii will even more decrease the number of fibers which can be routed in the flexfoil. This can be achieved by a suitable production method of the flexfoil. For optical fiber flexfoils proper fiber routing and lamination techniques make this possible without raising any reliability issues, see the simultaneously filed U.S. patent applications “Applying an optical fiber to a substrate” and “Lamination of optical fiber flexfoils”. Instead of having fibers laminated in flexfoils, flexfoils having patterned polymer waveguides can be used.
For the board application tabs obtained from cut-outs and not projecting beyond the flexfoils edges are not required as such but may constitute an advantage for both routability and manufacturability. The manufacturing advantage is also true for the back plane case.
For routing there is more undisturbed flexfoil routable area left in the case where the tabs are external, i.e. projecting from the flexfoil edges, compared to the case of having a flexfoil comprising a plurality of strictly internal tabs being mounted in parallel to, at the large surface of a conventional circuit pattern board. However, the total routing area may be significantly smaller in the first case since per definition external tabs implies that the usually rectangular flexfoil will have to be smaller than the electric board, but for tabs having arbitrary locations the flexfoil can have the same size as the circuit board. Also, the arbitrary tab locations allow that corresponding optical connectors of the circuit board can be located with less restrictions since they must not then be located at the board edges. However, the importance of this may be limited to particular cases.
For internal tabs in fiber floxfoils to be practical, a fiber layout scheme which is not continuous—a continuous depositing process is described in the cited AT&T patent—but which can cut the fiber and restart at several positions is a definite advantage, since else there will be a plentitude of redundant loose fiber strands deposited on the flexfoil.
Engberg Kristian
Hesselbom Hjalmar
Robertsson Mats
Bovernick Rodney
Burns Doane Swecker & Mathis L.L.P.
Kim Ellen E.
Telefonaktiebolaget LM Ericsson (publ)
LandOfFree
Flexfoils having connector tabs does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flexfoils having connector tabs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flexfoils having connector tabs will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438487